The present invention relates to a loudspeaker installed in an automobile.
Mounting restrictions of automotive interior impose various limits on the installation of a car speaker. In other words, problems peculiar to the car speakers but not to home speakers arise. One of these problems is that a dip caused by reflected sound appears in the frequency response of the speaker.
Referring to FIG. 10, a conventional loudspeaker has a magnetic circuit 1 and a speaker frame 2, an opening of which is covered with a net 4 through a grille 3. The speaker is mounted on a rear tray 6 behind a rear seat 5 so that the axis of the speaker is set in the vertical direction. As a result, the opening of the speaker frame 2 faces a rear window 7. Sound from the speaker is propagated through the interior space of the automobile to a listener 8.
In the conventional speaker, the sound which is transmitted to the listener 8 comprises a directly propagating sound .gamma. and a reflected sound (.beta.+.alpha.). There is a difference of time (.alpha.+.beta.-.gamma.)/c (c is the speed of sound between the direct sound .gamma. and the reflected sound (.beta.+.alpha.). Therefore, a dip appears near 500 Hz in the frequency response shown in FIG. 11. The dip prevents a clear sound reproduction.